1. Field of the Invention
This invention relates to improvements in a so-called Rzeppa type uniform universal joint which is provided with an outer member, an inner member, a plurality of balls retained in each opposed pair of a plurality of arcuate grooves formed lengthwise in the inner and outer surfaces of the two members for transmitting a torque between the two members, and a cage receiving the balls, and in which the centers of the arcs of the bottoms of the arcuate grooves of the two members are offset by substantially equal amounts on the opposite sides of the central plane of the joint. The invention is particularly concerned with a constant velocity universal joint suitable for mass production and having increased strength when the joint angle is large, while avoiding adverse effects when the joint angle is small, thereby prolonging the life of the joint.
2. Description of the Prior Art
In the recent years, FF of passenger cars have sharply progressed, and especially there is a tendency that four-wheel drive vehicles are increasing, in number. With the increasing demand for four-wheel drive vehicles, constant velocity universal joints operable at a large joint angle and high in strength and durability have become desired. Where the joint angle is large, that is, where the joint is bent greatly, there occur differences between the loads borne by the balls for transmitting a torque, and the load of a given ball my be substantially increased. Therefore, the forces exerted on the pockets of the cage become non-uniform and in conventional joints, this may cause the pocket portion of the cage to crack and flaking to occur near the shoulders of the grooves of the inner member which are adjacent to that side on which the groove wedge is narrow, moreover brinelling may be caused in the same region by a shock torque so as to cause abnormal noises and in addition, the balls can contact the corners of the pockets of the cage to create an edge load which may damage the balls or may deform and break down the corners of the pockets. The groove wedge refers to the angle formed by the bottoms of the lengthwise grooves formed in the outer and inner members.
An example of a device intended to overcome such disadvantages is the device of Japanese Utility Model Publication No. 53148/1981, but in this device, the centers of the spheres of the inner and outer spherical surfaces of the outer and inner members and the centers of the arcs of the bottoms of the lengthwise grooves are all offset by equal amounts. Therefore, the grooves are shallow at the small joint angle operation which is frequently used. Also, this leads to a short life, and the thickness of the cage is very large on that side on which the groove wedge is great, as will later be described, and therefore, the press work of the pocket has been difficult and the yield of the material is low. Thus this device has been unsuitable for mass production and has been costly.